302 



PLANT STUDIES 



\VvV 



^rh 



l^'n;. '-^Tli A common innsM 

 iJ'oh/frtr// 1/ III i-i'/iniiiiiii ). 

 eliowing tlie Icnfy gamcto- 

 phore with rhizoide (rh), 

 and two pp()roj)tiytcH (sporo- 

 goriia), witli f^cta (.v), calyp- 

 tra (r). and opLTCulum iii), 

 t\w. calyptra having been re- 

 moved.— After SCUENCK. 



l)laiit front wliich it came. 'J'']iis now 

 leafless Ijody consists of a slender 

 stalk betiring at its summit an iirn- 

 like case in wliich are developed nu- 

 merous asexiuxl spores (Figs. 370, 292). 

 This whole structure is often called 

 the "spore fruit," and its stalk is 

 imbedded at base in the summit of 

 the leafy branch, thus obtaining firm 

 anchorage and absorbing what nour- 

 ishment it needs, hut no more a part 

 of the leafy branch than is a para- 

 site a j)art of the host. 



When the asexual spores, pro- 

 duced by the '' sjiore fruit," germi- 

 nate, they reproduce the alga-like 

 liody with which we began, and the 

 life cycle is completed. 



In examining this life history, it 

 is api^arent that each spore produces 

 a dilfercnt structtire. I'he asexual 

 sjjore produces the alga-like body 

 with its erect letify branch, while 

 the oospore produces the " sjjore 

 fruit " with its leafless stalk and 

 spore case, l^hese two structures, 

 one produced by the asexual spore, 

 the other by tlie oospore, appear in 

 alternating succession, and this is 

 what is meant Ijy aller)ii(liiiii of i/ni- 

 crdfioiis. 



These two "generations" difl'er 

 strikingly from one another in the 

 s])ores wliich they produce. The 

 generation composed of alga -like 

 body aitd erect leafy branch jjro- 



